Most modem automotive fuel systems utilize fuel injectors to provide precise metering of fuel for introduction into each combustion chamber. Additionally, the fuel injector atomizes the fuel during injection, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected, and allowing the oxidizer, typically ambient air, to more thoroughly mix with the fuel prior to combustion. The precise metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine.
An electromagnetic fuel injector typically utilizes a solenoid assembly to supply an actuating force to a fuel-metering valve. Typically, the fuel metering valve is a plunger-style needle valve which reciprocates between a closed position, where the needle is seated in a valve seat to prevent fuel from escaping through a metering orifice into the combustion chamber, and an open position, where the needle is lifted from the valve seat, allowing fuel to discharge through the metering orifice for introduction into the combustion chamber.
Fuel flowing through a fuel injector typically exits at an outlet end of the fuel injector. The outlet end typically have a disk or plate with at least one orifice to control, in part, the spray pattern and the direction of the fuel exiting the fuel injector.
An orifice extending along an axis perpendicular to a surface of a work piece (i.e. a straight orifice) is believed to be formed by drilling or by punching through the work piece. One method of drilling is by electric discharge machining (EDM) that can form orifices of 150 to 200 microns in diameter. It is believed that one of the many disadvantages of EDM is the fact that the holes are typically formed without any favorable entry or exit geometry for the orifices, thereby affecting the flow through the orifices. Another method is by laser machining the orifices on the work piece or the plate. Yet another method can be by stamping or punching the orifices and then coining each edge of the orifice. However, it is believed that the orifices formed by these methods do not allow for spray targeting of the fuel as the fuel leaves the orifices of the injector.
In order to target the fuel spray, it is believed that orifices can be angled to a desired angle relative to a longitudinal axis of the fuel injector. Such angled orifices can be formed by any of the above methods, albeit at, it is believed, a much greater cost than a straight orifice. Another method utilizes dimpling a portion of the work piece on which a straight orifice has already been formed with a right circular cone. However, it is believed that such dimpled orifice plate increases a sac volume between the fuel injector closure tip and the orifice plate. This increased sac volume, during a non-injection event, causes fuel to remain in the sac that vaporizes and causes rich/lean shifts and hot start issues, which are undesirable.